Erm - a touch of the blind leading the blind here, 'cos I'm no technocrat. Doubtless one'll be along in a minute.
Meantime you could try downloading and installing the program again in case the copy on your system has got corrupted.
Also, I have not found RealPlayer at all user-friendly. There are heaps of alternatives. If you google CNET DOWNLOAD you'll find a few from a reliable virus-free source.